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1.
Older and more recent pieces of observational evidence suggest a strong connection between QSOs and galaxies; in particular, the recently discovered correlation between black hole and galactic bulge masses suggests that QSO activity is directly connected to the formation of galactic bulges. The cosmological problem of QSO formation is analysed in the framework of an analytical model for galaxy formation; for the first time a joint comparison with galaxy and QSO observables is performed. In this model it is assumed that the same physical variable that determines galaxy morphology is able to modulate the mass of the black hole responsible for QSO activity. Both halo spin and the occurrence of a major merger are considered as candidates for this role. The predictions of the model are compared with available data for the type-dependent galaxy mass functions, the star formation history of elliptical galaxies, the QSO luminosity function and its evolution (including the obscured objects contributing to the hard-X-ray background), the mass function of dormant black holes and the distribution of black hole-to-bulge mass ratios. A good agreement with observations is obtained if the halo spin modulates the efficiency of black hole formation, and if the galactic haloes at z =0 have shone in an inverted order with respect to the hierarchical one (i.e., stars and black holes in bigger galactic haloes have formed before those in smaller ones). This inversion of hierarchical order for galaxy formation, which reconciles galaxy formation with QSO evolution, is consistent with many pieces of observational evidence.  相似文献   

2.
We present evidence that there is a significant correlation between the fraction of the mass of a galaxy that lies in its central black hole and the age of the galactic stellar population. Since the absorption-line indices that are used to estimate the age are luminosity-weighted, they essentially measure the time since the last significant episode of star formation in the galaxy. The existence of this correlation is consistent with several theories of galaxy formation, including the currently favoured hierarchical picture of galaxy evolution, which predicts just such a relation between the black hole mass and the time since the last burst of merger-induced star formation. It is not consistent with models in which the massive black hole is primordial, and hence uncoupled from the stellar properties of the galaxy.  相似文献   

3.
The overabundance of Mg relative to Fe, observed in the nuclei of bright ellipticals, and its increase with galactic mass, poses a serious problem for all current models of galaxy formation. Here, we improve on the one-zone chemical evolution models for elliptical galaxies by taking into account positive feedback produced in the early stages of supermassive central black hole growth. We can account for both the observed correlation and the scatter if the observed anti-hierarchical behaviour of the AGN population couples to galaxy assembly and results in an enhancement of the star formation efficiency which is proportional to galactic mass. At low and intermediate galactic masses, however, a slower mode for star formation suffices to account for the observational properties.  相似文献   

4.
If supermassive black holes in centres of galaxies form by merging of black hole remnants of massive Population III stars, then there should be a few black holes of mass one or two orders of magnitude smaller than that of the central ones, orbiting around the centre of a typical galaxy. These black holes constitute a weak perturbation in the gravitational potential, which can generate wave phenomena in gas within a disc close to the centre of the galaxy. Here, we show that a single orbiting black hole generates a three-arm spiral pattern in the central gaseous disc. The density excess in the spiral arms in the disc reaches values of 3–12 per cent when the orbiting black hole is about 10 times less massive than the central black hole. Therefore, the observed density pattern in gas can be used as a signature in detecting the most massive orbiting black holes.  相似文献   

5.
Anisotropic emission of gravitational waves during the merger of black holes induces a recoil velocity on the centre of mass of the binary and the final merger product can then be ejected from its host galaxy. We consider ejected black holes which stay on bound orbits around their host haloes. A recoiled black hole which moves on an almost radial orbit outside the virial radius of its central galaxy, in the cold dark matter background, reaches its apapsis in a finite time. Due to small dark matter velocity dispersion at high redshifts and also the small black hole velocity near the apapsis passage a high-density wake forms around these black hole. Gamma-ray emission can result from the enhancement of dark matter annihilation in these wakes. The diffuse high-energy gamma-ray background from the ensemble of such black holes in the Hubble volume is also evaluated.  相似文献   

6.
The problem of few black holes becomes important in multiple mergers of galaxies. If supermassive black holes in centres of galaxies are common, then interaction of three or four supermassive black holes should also be common. The merger of two galaxies with one black hole each produces a semi-stable black hole binary system. Subsequent mergers of galaxies with their own central black holes produces dynamical few-body evolution in which mergers of black holes occur. According to our numerical simulations this evolution typically ends when only one or two black holes remain and, in the latter case, they are ejected in opposite directions from the center of the galaxy. Even when we pick the initial black hole masses at random from a wide distribution, the two black hole ejections happen rather symmetrically. Sometimes the final masses differ considerably in which case only the lighter black hole is ejected. This is caused by the potential barrier of the galaxy itself which prevents the heavy slowly moving black hole flying out of the galaxy. We discuss OJ287 as a possible example of a multiple black hole system.  相似文献   

7.
Strong evidence for the presence of a warped Keplerian accretion disc in NGC 4258 (M 106) has been inferred from the kinematics of water masers detected at subparsec scales. Assuming a power-law accretion disc and using constraints on the disc parameters derived from observational data, we have analysed the relativistic Bardeen–Petterson effect driven by a Kerr black hole as the potential physical mechanism responsible for the disc warping. We found that the Bardeen–Petterson radius is comparable to or smaller than the inner radius of the maser disc (independent of the allowed value for the black hole spin parameter). Numerical simulations for a wide range of physical conditions have shown that the evolution of a misaligned disc due to the Bardeen–Petterson torques usually produces an inner flat disc and a warped transition region with a smooth gradient in the tilt and twist angles. Since this structure is similar to that seen in NGC 4258, we propose that the Bardeen–Petterson effect may be responsible for the disc warping in this galaxy. We estimated the time-scale necessary for the disc inside of the Bardeen–Petterson radius to align with the black hole's equator, as a function of the black hole spin. Our results show that the Bardeen–Petterson effect can align the disc within a few billion years in the case of NGC 4258. Finally, we show that if the observed curvature of the outer anomalous arms in the galactic disc of NGC 4258 is associated with the precession of its radio jet/counterjet, then the Bardeen–Petterson effect can provide the required precession period.  相似文献   

8.
Evidence shows that massive black holes reside in most local galaxies. Studies have also established a number of relations between the MBH mass and properties of the host galaxy such as bulge mass and velocity dispersion. These results suggest that central MBHs, while much less massive than the host (~0.1%), are linked to the evolution of galactic structure. In hierarchical cosmologies, a single big galaxy today can be traced back to the stage when it was split up in hundreds of smaller components. Did MBH seeds form with the same efficiency in small proto-galaxies, or did their formation had to await the buildup of substantial galaxies with deeper potential wells? I briefly review here some of the physical processes that are conducive to the evolution of the massive black hole population. I will discuss black hole formation processes for ‘seed’ black holes that are likely to place at early cosmic epochs, and possible observational tests of these scenarios.  相似文献   

9.
We explore the relation between the linear length of radio core and the central black hole mass for a sample of radio-loud active galactic nuclei (AGNs). An empirical relation between the size of the broad line region (BLR) and optical luminosity is used to estimate the size of the BLR. The black hole mass is derived from H β linewidth and the radius of the BLR on the assumption that the clouds in BLRs are orbiting with Keplerian velocities. A significant intrinsic correlation is found between the linear length of the core and the black hole mass, which implies that the jet formation is closely related with the central black hole. We also find a strong correlation between the black hole mass and the core luminosity.  相似文献   

10.
Recent observations indicate that many if not all galaxies host massive central black holes. In this paper we explore the influence of black holes on the lensing properties. We model the lens as an isothermal ellipsoid with a finite core radius plus a central black hole. We show that the presence of the black hole substantially changes the critical curves and caustics. If the black hole mass is above a critical value, then it will completely suppress the central images for all source positions. Realistic central black holes are likely to have masses below this critical value. Even in such subcritical cases, the black hole can suppress the central image when the source is inside a zone of influence, which depends on the core radius and black hole mass. In the subcritical cases, an additional image may be created by the black hole in some regions, which for some radio lenses may be detectable with high-resolution and large dynamic range VLBI maps. The presence of central black holes should also be taken into account when one constrains the core radius from the lack of central images in gravitational lenses.  相似文献   

11.
Variability of active galactic nuclei is not well understood. One possible explanation is existence of supermassive binary black holes (SMBBH) in their centres. It is expected that major mergers are common in the Universe. It is expected that each supermassive black hole of every galaxy eventually finish as a SMBBH system in the core of newly formed galaxy. Here we model the emission line profiles of active galactic nuclei (AGN) assuming that the flux and emission line shape variations are induced by supermassive binary black hole systems (SMBBH). We assume that the accreting gas inside the circumbinary (CB) disk is photo ionized by mini accretion disk emission around each SMBBH. We calculate variations of emission line flux, shifts and shapes for different parameters of SMBBH orbits. We consider cases with different masses and inclinations for circular orbits and measure the effect to the shape of emission line profiles and flux variability.  相似文献   

12.
We have used the impulsive approximation technique to numerically estimate the effect of dynamical friction on the motion of a supermassive black hole (mass 109 M ) through a galaxy (mass=1011 M ) which has recoiled from the center of the latter as a result of anisotropic emission of gravitational radiation or asymmetric plasma emission. We find the effect to be minimal for recoil taking place at a velocity larger than that of escape at the center of the galaxy. There is a certain critical velocity of ejection (slightly larger than the central escape velocity) at which the black hole must be ejected for the recoil to be successful. Otherwise, dynamical friction becomes relatively pronounced and damped oscillatory motion of the black hole in the potential well of the galaxy ensues. The phenomenon of high-velocity recoil although rare, can be astrophysically spectacular in view of the fact that the black hole would carry a substantial amount of gaseous material as well as a very large number of galactic stars. Some recent observations are cited where the recoil phenomenon might be applicable.  相似文献   

13.
It has long been known that galaxy interactions are associated with enhanced star formation. In a companion paper, we explored this connection by applying a variety of statistics to Sloan Digital Sky Survey (SDSS) data. In particular, we showed that specific star formation rates of galaxies are higher if they have close neighbours. Here, we apply exactly the same techniques to active galactic nuclei (AGN) in the survey, showing that close neighbours are not associated with any similar enhancement of nuclear activity. Star formation is enhanced in AGN with close neighbours in exactly the same way as in inactive galaxies, but the accretion rate on to the black hole, as estimated from the extinction-corrected [O  iii ] luminosity, is not influenced by the presence or absence of companions. Previous work has shown that galaxies with more strongly accreting black holes contain more young stars in their inner regions. This leads us to conclude that star formation induced by a close companion and star formation associated with black hole accretion are distinct events. These events may be part of the same physical process, for example a merger, provided they are separated in time. In this case, accretion on to the black hole and its associated star formation would occur only after the two interacting galaxies have merged. The major caveat in this work is our assumption that the extinction-corrected [O  iii ] luminosity is a robust indicator of the bolometric luminosity of the central black hole. It is thus important to check our results using indicators of AGN activity at other wavelengths.  相似文献   

14.
We analyse the observed distribution of Eddington ratios  ( L / L Edd)  as a function of supermassive black hole mass for a large sample of nearby galaxies drawn from the Sloan Digital Sky Survey. We demonstrate that there are two distinct regimes of black hole growth in nearby galaxies. The first is associated with galaxies with significant star formation [   M */star formation rate (SFR) ∼  a Hubble time] in their central kiloparsec regions, and is characterized by a broad lognormal distribution of accretion rates peaked at a few per cent of the Eddington limit. In this regime, the Eddington ratio distribution is independent of the mass of the black hole and shows little dependence on the central stellar population of the galaxy. The second regime is associated with galaxies with old central stellar populations (   M */SFR ≫  a Hubble time), and is characterized by a power-law distribution function of Eddington ratios. In this regime, the time-averaged mass accretion rate on to black holes is proportional to the mass of stars in the galaxy bulge, with a constant of proportionality that depends on the mean stellar age of the stars. This result is once again independent of black hole mass. We show that both the slope of the power law and the decrease in the accretion rate on to black holes in old galaxies are consistent with population synthesis model predictions of the decline in stellar mass loss rates as a function of mean stellar age. Our results lead to a very simple picture of black hole growth in the local Universe. If the supply of cold gas in a galaxy bulge is plentiful, the black hole regulates its own growth at a rate that does not further depend on the properties of the interstellar medium. Once the gas runs out, black hole growth is regulated by the rate at which evolved stars lose their mass.  相似文献   

15.
I use the fact that the radiation emitted by the accretion disk of supermassive black hole can heat up the surrounding gas in the protogalaxy to achieve hydrostatic equilibrium during the galaxy formation. The correlation between the black hole mass M BH and velocity dispersion σ thus naturally arises. The result generally agrees with empirical fittings from observational data, even with M BH ≤106 M ⊙. This model provides a clear picture on how the properties of the galactic supermassive black holes are connected with the kinetic properties of the galactic bulges.  相似文献   

16.
If a massive neutrino halo transparent to light surrounds a compact body (galactic nucleus or black hole), then the strong gravitational field inside the halo will radically alter the spectral line profiles of a light-emitting Keplerian ring. This paper gives precise solutions of the spectral profile in a core-halo structure of matter and neutrino, and the result is compared with the no-halo case. The distribution of the neutrino mass is also given under typical circumstances.  相似文献   

17.
We consider a cosmological model in which part of the Universe, Ωh～10?5, is in the form of primordial black holes with masses of ～ 105 M ⊙. These primordial black holes were the centers for growing protogalaxies, which experienced multiple mergers with ordinary galaxies and with each other. The galaxy formation is accompanied by the merging and growth of central black holes in the galactic nuclei. We show that the recently discovered correlations between central black hole masses and galactic bulge parameters naturally arise in this scenario.  相似文献   

18.
The mass density of massive black holes observed locally is consistent with the hard X-ray background provided that most of the radiation produced during their growth was absorbed by surrounding gas. A simple model is proposed here for the formation of galaxy bulges and central black holes in which young spheroidal galaxies have a significant distributed component of cold dusty clouds, which accounts for the absorption. The central accreting black hole is assumed to emit both a quasar-like spectrum, which is absorbed by the surrounding gas, and a slow wind. The power in both is less than the Eddington limit for the black hole. The wind, however, exerts the most force on the gas and, as earlier suggested by Silk & Rees, when the black hole reaches a critical mass it is powerful enough to eject the cold gas from the galaxy, so terminating the growth of both black hole and galaxy. In the present model this point occurs when the Thomson depth in the surrounding gas has dropped to about unity and results in the mass of the black hole being proportional to the mass of the spheroid, with the normalization agreeing with that found for local galaxies by Magorrian et al. for reasonable wind parameters. The model predicts a new population of hard X-ray and submm sources at redshifts above 1, which are powered by black holes in their main growth phase.  相似文献   

19.
Central gravitational image detection is very important for the study of the mass distribution of the inner parts (∼100 pc) of lens galaxies. However, the detection of such images is extremely rare and difficult. We present a 1.7-GHz High Sensitivity Array (HSA) observation of the double-image radio lens system B1030+074. The data are combined with archive Very Long Baseline Array and global very long baseline interferometry (VLBI) observations, and careful consideration is given to the effects of noise, clean ing and self-calibration. An upper limit is derived for the strength of the central image of 180 μJy (90 per cent confidence level), considerably greater than would have been expected on the basis of a simple analysis. This gives a lower limit of ∼103 for the ratio of the brightest image to the central image. For cusped models of lens mass distributions, we have made use of this non-detection to constrain the relation between inner power-law slope β of the lensing galaxy mass profile, and its break radius r b. For   r b > 130 pc  the power-law slope is required to be close to isothermal  (β > 1.8)  . A flatter inner slope is allowed if a massive black hole is present at the centre of the lensing galaxy, but the effect of the black hole is small unless it is ∼10 times more massive than that implied by the relation between black hole mass and stellar velocity dispersion. By comparing four epochs of VLBI observations, we also detected possible superluminal motion in the jet in the brighter image A. The B jet remains unresolved, as expected from a simple lens model of the system.  相似文献   

20.
Using recently published estimates — based on high spatial resolution spectroscopy — of the mass M BH of nuclear black holes for a sample of nearby galaxies, we explore the dependence of galaxy nucleus emissivity at various wavelengths on M BH. We confirm an almost linear scaling of the black hole mass with the baryonic mass of the host spheroidal galaxy. A remarkably tight relationship is also found with both nuclear and total radio centimetric flux, with a very steep dependence of the radio flux on M BH ( P  ∝  M 2.5BH). The high-frequency radio power is thus a very good tracer of a supermassive black hole, and a good estimator of its mass. This, together with the lack of significant correlations with the low-energy X-ray and far-IR flux, supports the view that advection-dominated accretion is ruling the energy output in the low accretion rate regime. Using the tight dependence of total radio power on M BH and the rich statistics of radio emission of galaxies, we derive an estimate of the mass function of remnants in the nearby Universe. This is compared with current models of quasar and active galactic nucleus (AGN) activity and of the origin of the hard X-ray background (HXRB). As for the former, continuous long-lived AGN activity is excluded by the present data with high significance, whereas the assumption of a short-lived, possibly recurrent, activity pattern gives remarkable agreement. The presently estimated black hole mass function also implies that the HXRB has been produced by a numerous population (∼ 10−2 Mpc−3) of moderately massive ( M BH ∼ 107 M⊙) black holes.  相似文献   

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